Guest Post by Ira Glickstein
This series began with a mechanical analogy for the Atmospheric “Greenhouse Effect” and progressed a bit more deeply into Atmospheric Windows and Emission Spectra. In this posting, we consider the interaction between air molecules, including Nitrogen (N2), Oxygen (O2), Water Vapor (H2O) and Carbon Dioxide (CO2), with Photons of various wavelengths. This may help us visualize how energy, in the form of Photons radiated by the Sun and the Surface of the Earth, is absorbed and re-emited by Atmospheric molecules. 
DESCRIPTION OF THE GRAPHIC
The animated graphic has eight frames, as indicated by the counter in the lower right corner. Molecules are symbolized by letter pairs or triplets and Photons by ovals and arrows. The view is of a small portion of the cloud-free Atmosphere. (Thanks to WUWT commenter davidmhoffer for some of the ideas incorporated in this graphic.)
- During the daytime, Solar energy enters the Atmosphere in the form of Photons at wavelengths from about 0.1μ (micron – millionth of a meter) to 4μ, which is called “shortwave” radiation and is represented as ~1/2μ and symbolized as orange ovals. Most of this energy gets a free pass through the cloud-free Atmosphere. It continues down to the Surface of the Earth where some is reflected back by light areas (not shown in the animation) and where most is absorbed and warms the Surface.
- Since Earth’s temperature is well above absolute zero, both day and night, the Surface radiates Photons in all directions with the energy distributed approximately according to a “blackbody” at a given temperature. This energy is in the form of Photons at wavelengths from about 4μ to 50μ, which is called “longwave” radiation and is represented as ~7μ, ~10μ, and ~15μ and symbolized as violet, light blue, and purple ovals, respectively. The primary “greenhouse” gases (GHG) are Water Vapor (H2O) and Carbon Dioxide (CO2). The ~7μ Photon is absorbed by an H2O molecule because Water Vapor has an absorption peak in that region, the ~10μ Photon gets a free pass because neither H2O nor CO2 absorb strongly in that region, and one of the 15μ Photons gets absorbed by an H2O molecule while the other gets absorbed by a CO2 molecule because these gases have absorption peaks in that region.
- The absorbed Photons raise the energy level of their respective molecules (symbolized by red outlines).
- The energized molecules re-emit the Photons in random directions, some upwards, some downwards, and some sideways. Some of the re-emitted Photons make their way out to Space and their energy is lost there, others back down to the Surface where their energy is absorbed, further heating the Earth, and others travel through the Atmosphere for a random distance until they encounter another GHG molecule.
- This frame and the next two illustrate another way Photons are emitted, namely due to collisions between energized GHG molecules and other air molecules. As in frame (2) the Surface radiates Photons in all directions and various wavelengths.
- The Photons cause the GHG molecules to become energized and they speed up and collide with other gas molecules, energizing them. NOTE: In a gas, the molecules are in constant motion, moving in random directions at different speeds, colliding and bouncing off one another, etc. Indeed the “temperature” of a gas is something like the average speed of the molecules. In this animation, the gas molecules are fixed in position because it would be too confusing if they were all shown moving and because the speed of the Photons is so much greater than the speed of the molecules that they hardly move in the time indicated.
- The energized air molecules emit radiation at various wavelengths and in random directions, some upwards, some downwards, and some sideways. Some of the re-emitted Photons make their way out to Space and their energy is lost there, others back down to the Surface where their energy is absorbed, further heating the Earth, and others travel through the Atmosphere for a random distance until they encounter another GHG molecule.
- Having emitted the energy, the molecules cool down.
DISCUSSION
As in the other postings in this series, only radiation effects are considered because they are the key to understanding the Atmospheric “Greenhouse Effect”. I recognize that other effects are as important, and perhaps more so, in the overall heat balance of the Earth. These include clouds which reflect much of the Sun’s radiation back out to Space, and which, due to negative feedback, counteract Global Warming. Other effects include convection (wind, thunderstorms, …), precipitation (rain, snow) and conduction that are responsible for transferring energy from the Surface to the Atmosphere. It is also important to note that the Atmospheric “Greenhouse Effect” and a physical greenhouse are similar in that they both limit the rate of thermal energy flowing out of the system, but the mechanisms by which heat is retained are different. A greenhouse works primarily by preventing absorbed heat from leaving the structure through convection, i.e. sensible heat transport. The greenhouse effect heats the earth because greenhouse gases absorb outgoing radiative energy and re-emit some of it back towards earth.
That said, how does this visualization help us understand the issue of “CO2 sensitivity” which is the additional warming of the Earth Surface due to an increase in atmospheric CO2? Well, given a greater density of CO2 (and H2O) molecules in the air, there is a greater chance that a given photon will get absorbed. Stated differently, a given photon will travel a shorter distance, on average, before being absorbed by a GHG molecule and be re-emitted in a random direction, including downwards towards the Surface. That will result in more energy being recycled back to the Surface, increasing average temperatures a bit.
Tim Folkerts says:
April 7, 2011 at 3:25 pm
Let me make a slight variation of your situation. A beam of light shines on a mirror, and the beam bounces off. The beam hits a second mirror head-on and bounces straight back to the first mirror, so that 100% of the energy bounces back to the first mirror. This makes the spot 200% as bright!
———————————————————————————————–;
False.
You only had one light packet which you bounced off the mirror.
Producing a light packet from where the Sun doesn’t shine violates energy conservation.
But let’s assume there are two identical light packets and you send one towards the mirror which is reflected.
Then it’s still false.
In order to conserve energy, the light has to undergo a 180 degree phase change on the reflection boundary.
Instead of adding adding the amplitudes, you have to substract them.
It’s the a perfact candiate for the greenhouse warming conjecture.
I started with one hypothetical packet, then considered a beam of light from a series of pulses. With enough pulses, the photons from an earlier pulse will reflect back from the second mirror when the photons from a later pulse are arriving. This gives twice the number of photons arriving compared to when a single pulse is used. It is a little inexact to call this “twice as bright” since brightness is a perception, but there is twice as much energy arriving as there was without the second mirror reflecting the light back.
Phase change and coherence will affect details of constructive & destructive interference, but I really don’t think these details detract from the original supposition. If you prefer, consider the light source incoherent so we can average out all the interference effects. (Similarly, I’m not going to worry about diffraction effects. Classical “ray optics” will suffice here.)
Richard E Smith says:
April 7, 2011 at 1:26 pm
davidmhoffer, joel and phil (I think) have all derided my experiment of reflecting the light from a spotlight back on to the wall where the spotlight is shining. They claim that the reflection from the mirror does add light to the bright spot but that it simply cannot be observed by the human eye. In other words they believe that reflecting light adds to the light from the source.
That’s your fault for designing a crappy experiment, and you’re too dumb to realize that your hypothetical result shows that all the reflected light is absorbed which doesn’t exactly support your view of GHE does it? It’s not that the light can not be observed by the human eye, it’s that it’s incapable of the quantitative response you claim. Try covering the mirror with a red (or blue or green) filter, does the bright spot appear redder (or bluer or greener) when reflected light is directed on it? You claim not.
For all those “cold things can’t heat warm things” people:
How does a freezer work? Mine is pretty much room temperature on the outside, at the back there’s a pretty warm spot, and inside it gets very cold. Let’s say it hasn’t been running, it is room temperature inside and out. I put something in it (we’ll call it the Thing) at room temperature (20C), turn on the freezer, and after a while we check and the thing is frozen an at -5C.
Now since the Thing started out at room temperature, and the outside of the freezer is still at room temperature, and the back is ABOVE room temperature, how did the Thing get cold? We know it is radiating energy, but where did it go? Since we “know” that cold things can’t transfer heat to warm things, and the outside of the freezer is clearly a lot warmer than the Thing, how did that happen? Did the warm outside of the freezer spray the inside with negatrons? Inversawatts? Snotohp (reverse of photons)? What? If cold things cannot radiate energy to warm things, how did the Thing get cold? Where did its watts go, since EVERYTHING AROUND IT IS WARMER THAN IT IS? If it had NOWHERE that it could send its watts because EVERYTHING around it was warmer, they would have had to stay in the Thing. But we know they didn’t, because the Thing isn’t just a little cooler than what it is surrounded by, it is -5C, 25 degrees colder. What did that cold thing do with all that energy it no longer has?
Unless…. good gosh…. no, it isn’t possible… unless it transferred its heat energy to…something warmer than itself? No…not possible….must be another explanation….
OOPS THERE ISN’T!
Just askin’.
“And, this differs from the greenhouse effect how exactly? The greenhouse effect says that additional CO2 makes the atmosphere a better insulator. Hence, less heat is needed to reach the same surface temperature.”
Joel
This is not as I understand the GHG theory.
And isn’t there a big difference between CO2 reducing the rate of cooling. And this
“The surface of the Earth is warmer than it would be in the absence of an atmosphere because it receives energy from two sources: the Sun and the atmosphere”
I find your referenced web site confusing. And comments like this
“Curiously, the surface of the Earth receives nearly twice as much energy from the atmosphere as it does from the Sun”.
Surely this is complete nonsense. How can the sun heat the earth then the earth releases energy and twice as much comes back.
Richard E Smith says:
April 7, 2011 at 1:26 pm
Ok then. Assume that a torch is shining on a purely reflective surface – the opposite of a blackbody. 100% of the light will be reflected. Now get a mirror and hold it over the reflective surface. Let’s assume that the mirror reflects 10% of the light leaving the surface back to the surface. That’s now an extra 10% to add to the light from the torch. So according to david and joel 110% of the original supply is now being emitted from the surface. Add a few more mirrors and you can keep on increasing the brightness. Are you really suggesting that you can create energy like this? What about the first law of thermodynamics? – energy can neither be created nor destroyed.
No energy is being emitted from the surface since none is being absorbed! No energy is being created, just recycled, just like in multipass cells. By the way I’d be interested in where you propose putting the second (and subsequent mirror), interesting trick if you can pull it off. I guess you haven’t worked much with optics.
Agile Aspect says:
Phase changes don’t have to do with conservation of energy. They have to with satisfying the boundary conditions. Light can have a 180 deg phase change upon reflection or no phase on reflection depending on whether the material it is hitting has a higher or lower refractive index, respectively. Or, if the object is a metal and has a complex refractive index (meaning it absorbs light) then the phase change angle doesn’t have to be either 180 deg or 0 deg.
And, as Tim noted, you can talk about incoherent light.
RJ says:
No…It just means that there are different ways of looking at the same thing. The reducing the rate of cooling is the net result. The details about how this comes about involve the exchange of radiation.
You can’t just invent laws of physics because they sound plausible to you. You have to consider what the actual Laws of Physics say. A good example of this is a quiz question I recently gave my students. They had to choose which statement was NOT a consequence of the 2nd Law. The correct answer was: “A heat pump cannot pump more heat from a cold to a hot reservoir than the amount of work that is used to run it.” However, the majority did not choose this statement because it sounds like such a plausible consequence of the 2nd law, never mind that it is dead wrong. Nearly all practical heat pumps do in fact pump more heat than the work used to run them. In fact, as the two temperatures get closer together, the amount of heat one can pump from the cold to hot reservoir for a given amount of work gets larger and larger.
What the Laws of Physics say for the situation we are discussing is that in steady-state, the rate of energy absorbed and emitted by an object have to be equal. If the earth is receiving power from both the sun and the atmosphere, then it can indeed radiate more than it received from the sun. In fact, on Venus, this is taken to an extreme…I think the amount of radiation that the surface receives directly from the sun is only a few percent of the amount that the hot surface emits.
davidmhoffer says:
I think I am going to have to argue with you on this one. A freezer is a heat pump. That is, it uses work (provided by electrical energy) to “pump heat” in the opposite direction than it naturally wants to flow, just as a mechanical pump can make water go uphill. So, the reason the object gets colder when you put it in the freezer is that the refrigerant pipes do cool the freezer so it is colder than the object and then heat flows from the object to the refrigerant.
However, what is true about your example is that the object in the freezer is always radiating…It doesn’t magically start to radiate only once you turn it on and the refrigerant gets cold enough. It is just that the walls are radiating back as much or more than the object is radiating to them until the refrigerant gets cold enough. (There is also conduction and convection involved but I am simplifying the wording here…Imagine you have a perfect-vaccuum-freezer.)
It is actually true that in the absence of applied work, heat will not spontaneously go from a hotter object to a colder object. And, even within the freezer itself, the spontaneous flows from, say, the object to the refrigerant will be from hotter to colder. However, “heat” is a macroscopic concept and the reason heat flow must be from hotter to colder is due to the constraints imposed by the statistical physics. On a microscopic scales, the laws of physics involved are reversible. Applied to radiation, what this means is that a colder object will always absorb more radiation from a hotter object than the hotter object absorbs from the colder. Hence the heat flow will be from hotter to colder.
What it does not say is that there is no radiation from the colder that is absorbed by the hotter. That is the “Magical Second Law of Thermodynamics” rearing its head.
Joel Shore says:
“The reducing the rate of cooling is the net result.”
More anti-science. Just how would the imagined reduction of the rate of cooling be falsified? Or even empirically quantified?
Once again, the inconvenient scientific method is ignored by pseudo-scientists.
Smokey says:
April 8, 2011 at 9:24 am
Joel Shore says:
“The reducing the rate of cooling is the net result.”
More anti-science. Just how would the imagined reduction of the rate of cooling be falsified? Or even empirically quantified?
Once again, the inconvenient scientific method is ignored by pseudo-scientists.
Smokey;
You know who I am and you know my opinions on CAGW, so please sit down before you read this:
You haven’t been following this thread I presume, but Joel is 100% correct here.
Joel – I think one of your responses was poorly worded. By saying the surface of the earth is heated by two sources, one the sun the other the atmosphere, I think you gave one of those technicaly right but gives the wrong impression answers. Better would have been something like the surface is heated directed by the sun, and directly by the atmosphere, but the atmosphere is really second hand sun. The second hand sun w/m2 are bigger than the direct sun w/m2.
Smokey says:
April 8, 2011 at 9:24 am
Joel Shore says:
“The reducing the rate of cooling is the net result.”
Once again, the inconvenient scientific method is ignored by pseudo-scientists.
Smokey;
You know who I am and you know my opinions, so please sit down before you read this:
You haven’t been following this thread I presume, but Joel is 100% correct here.
Joel – I think one of your responses was poorly worded. By saying the surface of the earth is heated by two sources, one the sun the other the atmosphere, I think you gave one of those technicaly right but gives the wrong impression answers. The Sun heats directly with s/w, and indirectly with l/w. But the source of the watts in both cases is the Sun.
Smokey says: April 8, 2011 at 9:24 am
“More anti-science. Just how would the imagined reduction of the rate of cooling be falsified? Or even empirically quantified?”
That’s a lot like asking “How would the imagined reduction of the rate of cooling for a covered pot compared to a similar uncovered pot be falsified?” Well, you could try do the experiment and finding a case where a covered pot cooled more quickly that a similar uncovered pot. Good luck with that.
Similarly, the GHGs have been shown experimentally and theoretically to keep the earth warm. Good luck finding a counterexample to disprove this.
That said, it is certainly possible that OTHER effects might tend to counteract this. If the uncovered pot was insulated on the other sides (perhaps a thick ceramic) then it might cool more slowly DESPITE the fact it was uncovered. If the earth had more clouds to reflect away incoming light, it might cool DESPITE the fact that GHGs are helping keep it warm.
“Everything else being equal, increasingCO2 will result in increased surface temperature” could in principle be falsified (but again, good luck with that). I don’t see how (everything else being equal), that more energy to the surface (in the form of IR from the atmosphere) could have no effect or a cooling effect.
“If other mechanisms are considered, increasing CO2 will result in increase the surface temperature” could be falsified, and you have a much better chance here because now other competing effects could come into play. Indeed, since CO2 has been monotonically increasing for decades but temperature has not, we can safely claim that there MUST BE other affects besides CO2. More CO2 could lead to more clouds, which reflect away more might and help to cool the surface. Upwelling cold water from the oceans could help to cool the surface. The sun could dim and help to cool the surface….
Now we have LOTS of hypotheses to falsify, some where you have a good shot at success!
davidmhoffer,
You are right, I’ve not read nearly this entire thread. So are you saying, like Trenberth claims, that the reason there has been no CAGW is that there is empirical [ie: real world, testable, quantifiable, falsifiable and reproducible] evidence, per the scientific method, showing the amount of cooling that supposedly offsets global warming?
If so, please demonstrate it. I’ve been wrong before, and if I’m wrong I will acknowledge it. Maybe I just missed that particular evidence.☺
davidmhoffer say:
I don’t disagree with you really. I was actually giving what Alistair Fraser gives as his preferred explanation. (I suggest reading his “Bad Greenhouse” piece and accompanying FAQ.) He is very militant about making technically-correct statements, so he doesn’t like any terminology like the atmosphere reflecting IR (which I think we all agree with) but also like “back-radiation” or “re-radiation”. His point is simply that it radiates because it has a temperature, not specifically because it has absorbed a photon. I tend to agree with you that his extreme militancy in avoiding any incorrect implications means that you sort of lose the bigger picture…i.e., the atmosphere has a temperature because of the radiation that it absorbs directly from the sun (to a small degree) and the radiation it absorbs from the earth that is due to energy that originally came from the sun.
Tim Folkerts,
If a conjecture like Trenberth’s cannot be falsified, then the process ends at Conjecture. There is no testable Hypothesis that follows. No wonder Trenberth says he wants to nullify the null hypothesis. It falsifies his alternate CAGW conjecture. Kevin Trenberth is to science as astrology is to astronomy.
Either you accept the scientific method, or you don’t. There is no fuzzy in-between gray area. The scientific method is rigorous for a good reason. Fuzzy post-normal ‘science’ tries to evade rigor, which places it in the same category as Scientology.
And I would remind you that global warming is not in dispute by about 98.5% of those posting here [my WAG/observation], and that I am one of the 98.5%. The important questions are:
1. Does human emitted CO2 cause measurable global warming?
2. If so, what is the empirically measured amount of that warming?
3. Has the rise in CO2 caused any measurable, testable evidence of global damage?
The answer to #3 is by far the most important in the entire debate, because if CO2 is observed to be harmless, then there is no reason to continue shoveling taxpayers’ money at a trumped-up non-problem.
The rest of the debate over the greenhouse effect, etc., is just wild-eyed arm waving intended to demonize “carbon”, and deny perfectly natural climate cycles in order to advance an agenda. That is not science; that is advocacy.
davidmhoffer uses the example of a fridge to demonstrate that cooler things can warm warmer things. I presume that David is not denying the second law of thermodynamics and knows very well that a cold thing can only warm a warmer thing if energy is provided – a pump in the case of refrigerator. If you switch the fridge off the frozen chicken warms up in demonstration of the second law.
David also claims that in admitting that there is such a thing as insulation I am contradicting myself because that is what the greenhouse effect is – a form of radiative insulation. But insulation cannot make a blackbody which is absorbing and emitting all the energy it is receiving reach a higher temperature. The greenhouse effect is demonstrated by constant-irradiance models – the Sun is always shining a constant quantity and the Earth is not cooling down (there is no night). Furthermore the Earth emits as much radiation out to space as it receives. So it appears that according to greenhouse theory greenhouse gases manage to restrict radiation and release it at the same time.
David, Joel and others say that the trapping of heat or back-radiation provides the extra heat. So here is the nub of the debate. Can the return of radiation to the source heat up the source? According to them it can. Therefore a 1kw radiant heater will emit 2kw if its emissions are reflected directly back to it. What about two 1kw heaters emitting 1kw directly to each other? Presumably they then emit 2kw each.
As this seems to contradict the law of conservation of energy I take exception to the view that I must be espousing some sort of religious belief. In Professor Robert Wood’s experiment with two enclosures – one with glass and one with halite – he found that, contrary to expectations, the temperature in the glass enclosure was cooler because the glass excluded some of the infra-red part of the spectrum of the sunlight, whereas the halite did not. Only when he placed glass over the halite did the temperatures match – and there was scarcely a difference of a degree between them. Heat trapping was not demonstrated.
The radiation a body emits is a function of its temperature. Greenhouse theory makes temperature a function of how much radiation a body emits.
Step 2.5
Chicken rises in temperature until it is radiating 300 watts.
Oven absorbs 300 watts.
Oven rises in temperature until it is radiating 300 watts, 150 inward and 150 outward.
Nope. Did it in my radar range the walls never got hot the air did not get hot only the chicken got hot from all the excited water molecules moving so much.
mkelly – you don’t have a radar range, you have a microwave oven. You have no way of measuring the temperature of the inner walls while it is running, nor do you understand the difference between an example to illustrate an issue and the order of magnitude of the numbers you would need to measure to quantify a real world example.
smokey – it isn’t about Trenberth’s processes as he describes them, it is about the order of magnitude and the manner in which all the processes affect each other
richard e smith – good lord man, the pump puts energy into the WARM thing which is the freezer. Are you now going to try and explain how putting more watts into the warm freezer makes something else cold without that something else sending some heat energy out of itself to the only place it can – the warmer freezer? Are you even thinking about your answer before you spout off about it? your pathetic diatribe about multiple heaters shows how much you have retained from this discussion so far. Nothing.
There’s all sorts of gaping holes in the AGW theory that have merit and are worth the time to explain to people to make a mockery of the likes of Trenberth, Mann, Jones, Hansen and Briffa. But cockamamy arguments based on complete misunderstandings and total lack of math skills by idiotic experts who cannot take the time to read and comprehend that this particular issues has been documented ad naseum by the likes of Einseting, Stefan, Boltzman, Wiens, Millikan, Planck, has been reproduced by scientists in Japan, Russia, and China with no knowledge that others were working on the same things and yet arrived at the exact same equations, I no longer have time or patience for. Wallow in your own ignorance.
“David, Joel and others say that the trapping of heat or back-radiation provides the extra heat. So here is the nub of the debate. Can the return of radiation to the source heat up the source? According to them it can. Therefore a 1kw radiant heater will emit 2kw if its emissions are reflected directly back to it”
And then wouldn’t the 2kw further rise to 4kw etc.
I’m still trying to get my head around it all but surely experiments have been done to test this. For example including a heater in O2 then the same heater in CO2. Shouldn’t the heat source become hotter if it is in a container of CO2 compared to O2. In CO2 the heat source should increase by a noticeable amount due to back radiation
Or have I somehow missed the point. I can not see how the GHG back radiation theory can not be easily tested.
Richard E Smith says:
Yes…That was a bad example on his part. I corrected him in a post that has vanished (presumably into the SPAM filter but will hopefully be rescued eventually).
Yes…It can and must. The (steady-state) temperature is determined by having to have a balance between the incoming and outgoing energy.
The greenhouse effect is demonstrated in a variety of different models ranging from simple radiative shell models to full-blown models with everything but the kitchen sink thrown in.
If you were to instantaneously increase the quantity of greenhouse gases, then the earth would emit less radiation than it receives. This would then cause it to heat up until it was again emitting as much radiation as it received (because emission increases with temperature). That is the greenhouse effect.
Right now, greenhouse gas levels are changing fast enough for the earth to be a bit out of radiative balance, although only by a fraction of a W/m^2.
It is not some magical “return of radiation”. It is just the fact that some of the radiation from the earth is absorbed by the atmosphere. Because of this heat input, the atmosphere acquires a certain non-zero temperature and everything at non-zero temperatures radiate. Only the “Magical Second Law of Thermodynamics” says they don’t, a law for which there is no experimental evidence.
That means that you understand what conservation of energy says….Or, you are not able to see your way through the problem enough to understand what is going on. I recommend reading up on some simple models of the greenhouse effect (like Willis’s “steel greenhouse” so you understand how it works and how energy conservation is obeyed. Ultimately, you don’t test energy conservation by talking off the top of your head…You do it by writing down simple models of the phenomena, the known physical equations that describe them, and solving the equations. If you are not up to that task, then you at least have to read the exposition of someone who is. Otherwise you are just talking about something that you know nothing about and your opinion is frankly worthless.
Wood did not understand that the lapse rate is an important factor in the whole thing, something that in fact was not generally appreciated until about the 1950s (although one person in Wood’s time did apparently note this in a paper that Wood apparently was not aware of). He would need a really tall greenhouse to demonstrate the effect.
No, standard radiative transfer theory (and in fact heat transfer theory in general) says that the steady-state temperature is determined by the balance of energy in and energy out.
Smokey,
I agree with much of what you say.
*A hypothesis/theory/law must always be falsifiable to count as science. At some point, however, an idea can become so well established that doubting it becomes almost perverse (aka “extraordinary claims require extraordinary evidence”). Conservation of energy falls into this category. A heliocentric model of the solar system falls in this category.
I don’t think that Trenberth is trying to “nullify the null hypothesis” as much as he is trying to argue that AGW is so well established that the burden of proof is now on the other side. I think he is jumping the gun and overstating the certainty of AGW, but that does not per se make it unscientific.
As to your questions, let me add a little
0) Do GHGs as a whole warm the earth (ie is the GH effect real)?
I would say definitely yes. I’m a little surprised to see you say “the debate over the greenhouse effect, etc., is just wild-eyed arm waving”. The GH effect is a very scientific question and involves a lot of science. OTOH, how to RESPOND does indeed involve a bit of wild-eyes arm waving.
1a) Has CO2 increased because of human activity.
I would definitely agree with 1a). The quantities, timing, and isotopes point to fossil fuel use.
1b) Has human-caused CO2 caused measurable global warming?
2. If so, what is the empirically measured amount of that warming?
This is difficult because there is no conceivable way to do a controlled experiment. We only have one earth and we can’t control all the variables. This means the results must be based predominantly on calculations and theory, not on reproducible experiments of the type normally used to statistically test a null hypothesis.
If you accept (0) above (GHG’s have some effect), then the extension that more GHGs have more effect is logical. Decreased energy from the atmosphere to space consistent with “trapping” of energy due to CO2 have been measured. But since I can’t measure a “control earth”, I will not be able to give you the two side-by-side numbers.
3. Has the rise in CO2 caused any measurable, testable evidence of global damage?
Yes, that is the $64,000 question (or $64 trillion question)! I think that many scientist do themselves and the rest of us a disservice by venturing so far into advocacy. The line that Gore used works both ways: “It is difficult to get a man to understand something, when his salary depends upon his not understanding it!” (Upton Sinclair)
P.S. The link you had for “Hypothesis” was interesting. I do find it amusing that the author presents what he would call a conjecture (“Since the start of the Industrial era, Earth has been warming in recovery from these three events.”) as if it were an established fact. 🙂
Tim Folkerts,
Thanks for your comments. I don’t think we’re very far apart. The key question is still #3.
Some folks look at CO2 and see a dangerous threat. Others look at CO2 and see a harmless, beneficial trace gas that has been almost twenty times higher in the past, during times when life flourished. The scientific method is the accepted method to determine which view of reality is correct. When people ignore the scientific method, they generally arrive at the wrong conclusions.
Finally, there is Trenberth’s nemesis: the null hypothesis of natural climate variability [which he has demanded to be allowed to unilaterally change]. The null hypothesis falsifies claims made on behalf of the alternative hypothesis of catastrophic AGW due to the rise in CO2 [CO2=CAGW].
But no such CO2-caused catastrophe has happened in the geologic past, nor is any catastrophe currently evident, nor is a catastrophe on the horizon. The planet is still emerging from the LIA [and from the great stadial prior to the Holocene]. If we are using the scientific method, then we need more than evidence-free conjectures of impending global harm from what is really just another cyclical rise in a beneficial, minor trace gas – a rise that in the past has always followed temperature rises, rather than causing them.
If “this time it’s different,” then we must abide by the scientific method and insist upon convincing evidence – or reject that assumption as a baseless conjecture.
richardesmith says:
davidmhoffer says:
So that we don’t get sidetracked on this freezer thing, please read this post of mine that has now appeared:
http://wattsupwiththat.com/2011/03/29/visualizing-the-greenhouse-effect-molecules-and-photons/#comment-638179 (It may be pretty much the same thing you [David] are saying but frankly I am not quite following exactly what you are saying here.)
The Second Law does indeed say that heat flows from hot to cold (in the absence of work to move it from cold to hot). However, this is a statement about macroscopic systems that comes about not because of, but in spite of, the fact that the microscopic dynamics are reversible. That’s what makes the 2nd Law interesting…And, in some sense it was gives a direction to time. So, for example, suppose you have a box split in two by a flexible barrier and each side contains gas at a different temperature. Collisions of the molecules on the different sides of the flexible barrier will result in exchanges of energy between the molecules. Sometimes these collisions will actually cause the gas molecule on the “hot side” to gain energy and the one on the “cold side” to lose energy; however, more often it will be the other way around (for simple statistical reasons, i.e., that the molecules on the hot side have a higher velocity on average than those on the cold side)…And, when you are dealing with systems that have, say, 10^20 molecules, it becomes exponentially unlikely that you will ever observe the hot side getting hotter and the cold getting cooler on this macroscopic scale.
Applied to radiative heat transfer, what the 2nd Law says is that, although a cold object and hot object both radiate and both absorb radiation, on any macroscopic scale the cold object will always be observed to absorb more radiation from the hot object than the hot object from the cold object. It turns out that in order for this to be the case, a surface’s emissivity for a particular wavelength has to be equal to its absorptivity at that wavelength (Kirchhoff’s Law)…a fact that is indeed observed.
If you use the Laws of Radiative Transfer, including Kirchhoff’s Law, you will always get a result that agrees with the 2nd Law. There is no reason to build in arbitrary rules about what radiates toward what or any other such nonsense.
I think it is important to understand how the 2nd Law arises in the transition from the microscopic to macroscopic scale in order not to be fooled by statements of the “Magical 2nd Law of Thermodynamics” that try to tell you that certain things can’t happen which, in fact, can and do happen.
Tim Folkerts says:
April 6, 2011 at 12:21 pm
“I had to go doublecheck what I said …
I should amend that — the thermal radiation from the earth will infinitesimally help warm the sun, but the greenhouse effect will not matter… but there is always SOME small amount of energy and the near side would always be some infinitesimal amount warmer than the far side.
the total energy heading toward the sun will be essentially unchanged as GHG’s increase, the effect on the sun will be unchanged.”
The energy falling on earth is very small compared to the sun’s total radiation, but still we heat up to 288 K. Comparing amounts isn’t going to change the physics. The greenhouse effect itself is magnitudes smaller than the radiation we get from the sun, so is it to be ignored?
If GHG’s heat up the surface, more radiation will return to the sun thus add energy and raise the temperature.